Skyline logging systems are cable logging systems used to harvest timber from hillsides too steep for tractor logging. Skyline logging systems utilize a carriage, similar to a trolley, to yard (move) logs from the location where they are felled to the landing (a location where the logs are concentrated for loading onto trucks). During the in-haul phase of the operation, the logs are carried above ground level. An intermediate support for the skyline may be employed where there is a rise or hump between the yarder and the location from which the logs are transported, to provide the necessary ground clearance.
Logging over an intermediate support has been performed since the early part of the present century. Since its inception it has been used with standing skyline systems. These are systems which operate with the skyline anchored at one end while the other end is held in position with a brake for the entire setting. Once the skyline is laid in the intermediate support and raised into position, it does not move longitudinally in the support. Thus, in the previously employed systems the intermediate support engages a stationary line.
In modern systems, the haulback line is utilized to support both the carriage and the turn of logs. Therefore if an intermediate support is to be employed, it must support the haulback line, which always moves in a direction opposite to that of the carriage. There is a substantial need for an improved carriage and associated intermediate support structure which will sustain a moving line, such as a haulback line moving in a direction opposite to that of the carriage employed in the system, which will allow the carriage to smoothly pass the intermediate support while still providing the required support, even if the carriage tilts or swings transversely while passing, and which will retain the associated fast-moving and undulating cable.